The questioning was part of the committee's inquiry into hate crime and its violent consequences.

It comes as the German government proposed laws that would see tech companies fined up to £43m for not removing hate crime posts quickly enough.

Sky News understands that the UK Government is keeping a similar option under review.

The social media bosses defended their companies' actions, but Nick Pickles, head of public policy and government for Twitter, admitted the company was "not doing a good enough job".

He added that Twitter was trialling new technology to spot abusive and hate crime posts, but said: "The positive benefits our platforms bring - and technology brings - come with serious challenges.

"Yes, it brings out some of the worst in society but it brings to light things that we all rather did not happen.

"But the idea that you can preemptively detect things and remove them before they are posted, we're never going to get to that point."

Ms Cooper also said: "We understand the challenges that you face and technology changes very fast, but you all have millions of users in the United Kingdom and you make billions of pounds from these users, (but) you all have a terrible reputation among users for dealing swiftly with content even against your own community standards."